1. Field of the Invention
The present invention pertains to the field of noxious waste and residue treatment and relates more particularly to a method and an installation suited to the destruction of containers containing of laboratory wastes.
2. Description of the Prior Art
It is known that wastes and residues from various reactions and processing operations, generated in laboratories or small installations, are characterised by the fact that they are greatly varied in their composition and are produced in small unit quantities ranging, for example, from some hundreds of grams to a maximum of some kilograms. These wastes, which is most usually noxious or polluting substances, are generally collected in receptacles made of a variety of materials such as glass, composite materials, plastics, metal etc.
The handling operations known to date for getting rid of these wastes generally consist of opening the containers by hand, then analysing each set of contents if necessary and, finally, carrying out the treatment itself which needs to be adapted to each type and form (solid, liquid, powdery etc.) of waste.
These handling operations are very often extremely dangerous, notably during the opening of the receptacles which may allow toxic vapours to be exhaled or may contain products that are aggressive to the skin. They therefore call for infinite precaution and, in particular, require the wearing of special protective clothing. Furthermore, they entail substantial costs both in the numerous analyses needed and during the destructive treatment which has to be adapted to each particular case or group of wastes.
The main objective of the invention is to provide a method and an installation to implement this method, making it possible to overcome of all the above-mentioned drawbacks by eliminating any manual action or any prior analysis, by destroying the containers, automatically and recovering the destroyed materials, without any danger related to handling.
According to the principal and broadest definition of the method, the shock wave created by an explosion in a submerged medium is used to break containers such as flasks or similar containers holding dangerous products and wastes.
More precisely, the method according to the invention is one wherein the flasks, arranged in rows in baskets with metal grating, with interposed detonating fuses, are submerged in a basin and subjected to an explosion in relatively deep water, after which the baskets are lifted and subjected to a washing operation, the destroyed flasks being recycled or sent to the waste dump, while the wastes which have collected and/or have been gradually diluted in the basin are periodically removed and treated in a manner known manner.
It is known that the explosion, in water, of a detonating product is characterised by the creation of a shock wave and then the appearance of a pressure gas bubble. The shock wave conveys the maximum energy; however, the secondary pulsation pressures of the bubble have a more prolonged effect. It is precisely this type of explosion that is implemented to prompt the breakage of the containers of noxious wastes by using the shock waves that accompany the formation of gas bubbles. Since the operation is done in a submerged medium, the gases that may be generated during the breakage of the flasks are washed in the water of the basin. Furthermore, the gas currents produced when the bubbles break are used as means for the natural agitation of water in the basin or pool.
For the proper implementation of this method, it is appropriate to use explosive materials capable of withstanding submersion in pool water for at least one minute. An explosive such as penthrite is quite suited to this purpose but other materials that meet the above-mentioned condition are also suitable. An appropriate detonator is placed against the explosive fuse or fuses and it is necessary, as shall be explained further below, to determine, for each specific application, the maximum quantity of explosive and detonator required as a function of the volume of the pool and the number of flasks (or equivalent containers) to be treated in each blasting operation.
The depth to which the baskets of flasks and the associated detonating fuses must be submerged is a critical factor. Indeed, it is important that the gas bubble which is generated by the shock wave and which generally assumes a spherical shape should be able to break or burst on the surface of the water before attacking the wall of the basin so as to avoid the problems of pulsation of bubbles and, hence, to avoid the phenomena of resonance. It is also important to prevent excess pressure from being exerted on the walls of the basin through the expansion of gases. During trials carried out by the Applicant, and on the basis of the installation that shall be described hereinafter by way of an example, it has been determined that the depth of submersion should be at least one meter and that it is generally from one meter to 2.5 meters.